It's a good idea and has signal -- for now.

Just a matter of time until it's gamed with wash-zaps.

I was thinking of an un-gameable alternative. One idea is PoW. Would be cool, for example, if instead of the like count showing X likes, clients would include the total PoW of all reactions, like "X (Y PoW)". This way you can have "1 (20 PoW)" that has more weight than "20 (5 PoW)".